The current demand for electronic computers having greater speed and higher performance criteria creates stringent price-to-performance objectives which requires the use of existing packaging technologies. Two packaging technologies available today are metallized ceramic modules (MC) and multi-layer ceramic modules (MLC). As is known in the industry, MC modules comprise a ceramic substrate base on which a layer of metallized circuitry, which may be termed as a signal plane, is personalized and integrated circuit chips are conductively bonded to this circuit plane. MC modules are mounted on printed circuit cards and, as a result, they are limited in the number of input-output (I-O) connections that can be made; they introduce relatively large time delays in signal propagation; however, they are considered to be relatively inexpensive.
MLC modules comprise a ceramic substrate base on which more than one layer of metallized circuitry or signal plane is personalized and may also include a power or ground plane. These planes are separated by a dielectric material and plated-thru holes are used to electrically connect the planes to internal wiring. Integrated circuit chips are conductively bonded to the top metallized plane of the module. MLC modules are mounted on planar printed circuit boards and are therefore not limited in the number of I-O connections that can be made. Because MLC modules have relatively many more chips on the same module, lead lengths between chips are short. Therefore, signal propagation time delays are short. However, MLC modules are considered to be relatively expensive.
The packaging strategy for meeting price-to-performance objectives is to put that portion of the computing system which most affects the machine cycle time; namely, the logic, into MLC modules. The portion of the computing system which has less effect on machine cycle tiem; such as, the main memory, may be packaged in MC modules. Since price-to-performance dictates the use of two different types of modules within the same package, it is desirable to provide a special hybrid package configuration which will satisfy both the electrical requirements of planar and card-on-board connections and the mechanical requirements; such as, cooling.